In September-November 2012, we carried out an archaeological sounding in the sector of the Oppian Hill park above the outer surface of Trajanic Galleries 20A and 20B. The study was aimed at understanding the external layout and construction features of the ancient vaults, with a view both to reconstructing the missing parts and to defining the new external protection system for the monument. Below we publish the preliminary results of the archaeological study.
The galleries belong to a system of barrel-vaulted rooms built at the time of Trajan to subdivide the large open space of the Domus Aurea courtyard (Peristyle no. 20) and thus create the level area for the terrace of the Baths.
The two galleries studied are in a precarious state of conservation due above all to the loss of parts of the vaults in the past. They therefore form part of the conservation project for the NW corner of the Domus Aurea. This project entails structural consolidation, the reinstatement of continuity between the Neronian and Trajanic sectors and the microenvironmental isolation of the area.
Given the precarious state of conservation and the minimal thickness of the surviving vaults (about 15 cm at the crown), we needed to carry out some difficult propping work inside the two galleries to make it safe for artisans and archaeologists to enter the excavation area above.
The vaults of the Trajanic galleries are covered by a layer of earth about 1.20 m thick dating to the modern period, although it certainly consists in part of ancient stratigraphy, dug out and then replaced to raise the ground level to the park’s current height: inside this deposit are bone fragments, pottery sherds of the imperial and late imperial period together with evidently modern finds such as fragments of white enamelled ceramic plates and crockery. This accumulation shows that, at least in this area, the ancient layers have already been removed, perhaps to create the overlying park or during restoration work in the area during the late 1960s.
The surface brought to light by the removal of the earth layer, belonging to the exterior of the vaults of Trajanic Galleries 20A and 20B, presents a slight slope from south to north, from a height of 47.66 a.s.l. at the southern edge of the excavation to 47.49 a.s.l. at the northern edge. The concrete is characterized by the use of a fairly resistant pozzolana mortar and caementa consisting of medium-sized tufa chips.
An extremely interesting feature highlighted by the excavation is the identification of the “worksite phases” for the construction of the galleries and the connection between adjacent galleries:
after completing the construction of the perimeter walls of the various galleries (first phase) the wooden centering was put in place (second phase) on which concrete was cast to form the haunches of the vaults (third phase). Later a sort of abutment in earth and tufa chips was laid in the free space between the impost of one arch and the next, resting against that portion of the haunches that had previously been built (fourth phase).
This was followed by a further addition of concrete (fifth phase) which set onto the part of the vaults that had already been constructed, covering the earth abutment between adjacent vaults and forming a sort of screed linking the various galleries to one another.
The upper surface of this extremely smooth screed bears no traces of further floors above it, nor of the brick cavity found in other areas of the Trajanic terrace. From an altimetric point of view, on the other hand, the portion of outer surface brought to light (indicated on the plan by the letter L) which, as already said, has a height ranging from 47.66 to 47.49 a.s.l. is compatible with the similar surfaces found in soundings E, F and G opened in 2011 in the strip of park near today’s Via del Monte Oppio.
The excavation also brought to light a series of graves created by chiselling away the concrete of the Trajanic vaults. The burials are oriented east-west and are concentrated mainly near the haunches of the vaults, in other words where the structure is thickest. The subsequent conversion of the area into orchards and gardens led to the obliteration of the original ground surface from which the graves were dug, and the partial “mixing” of the original internal arrangement of the depositions, probably the origin of the bones found in the modern earth layer above. Of the only two tombs that have been fully excavated, Tomb 1 preserved the lower limbs and pelvis of an adult woman in a supine position, still anatomically connected.
Burial 2 yielded the severely compromised remains of an adult male skeleton, also in a supine position. In the absence of chronological indicators attributable with certainty to this funerary activity, it is not easy to give a precise date. Hypothetically, we can make a chronological and spatial correlation both with the tomb of the 5th-6th c. AD brought to light in Test Pit C and with the numerous burials (about 1000) of a similar date found in 1967 inside the so-called Sette Sale cistern.
Circular graves, rectangular depressions and linear grooves are further evidence of a new use of the area post-dating the establishment of the necropolis. These are fairly faint traces, also found inside the original Trajanic vaults, which seem to pave the way for a new arrangement of the area aimed at practices that we could describe as agricultural. These incisions suggest activities linked to the planting of trees or simple hedges.
A similar landscape can be ascribed to the system of vineyards and vegetable gardens attested on the Oppian Hill by the sources after the definitive abandonment of the Baths of Trajan.
The study was carried out under the Scientific direction of Elisabetta Segala and works management by Enrico del Fiacco; the excavation was carried out by Celis with archaeological assistance and documentation by the Cooperative Archeologia.